During the last twenty years, a very substantial amount of research has been effected into the improvement of, principally, the mechanical properties of flexible polymers by orientation. The required very high orientation of the molecular chains of flexible polymers, notably linear polyethylene, may be obtained either by preventing the formation of chain folded crystallites, as with precipitation from solution in an extensional flow regime, or by transforming a previously chain folded morphology into one comprising extended molecular chains, as with mechanical deformation: see, for example, our UK Patent Nos. 1480479 and 2060469B.
The latter class of procedures has the substantial advantage that, particularly in the case of filament spinning and drawing, existing industrial practice can integrate the procedures with comparatively small change. A disadvantage, however, notably in relation to polymeric stock of substantial cross-section is the amount of processing space necessarily required by the large deformation ratios which are dictated.
This invention seeks to provide a solid phase deformation process in which higher effective deformation, at given deformation ratios, than was hitherto available is manifest.